Production of chromium-bearing reaction mixtures and alloys



Patented May 27, 1 941 PRODUCTION OF CHROMIUM-BEARING RE- ACTION MIXTURES AND ALLOYS Marvin J. Udy, Niagara Falls, N. Y.

No Drawing. Application October 26, 1939, Serial-No. 301,375

20 Claims.

This invention relates to metallurgy and has for an object the provision of improved metallurgical processes and products. A particular object of the invention is to provide improved processes and products employing high-carbon ierrochromium. The invention further contemplates the provision of improved methods of employing high-carbon ferrochromi'um in the production of chromium-bearing iron and steel products. A further object of the invention is .to provide improved exothermic mixtures containing high-carbon ferrochromium and suitable oxidizing material, which mixtures are capable, upon ignition, of reacting within themselves with the development of sufilcient heat to melt the iron and chromium of the ferrochromium. A further important object of the invention is to provide reaction mixtures in the form of solid agglomerates comprising particles of high-carbon ferrochromium intimately associated with and bonded together by means of oxidizing material.

The invention contemplates the production and use of reaction mixtures comprising high-carbon ierrochromium and one or more oxidizing agents. The invention provides reaction mixtures containing high-carbon ferrochromslurn which are capable upon ignition of producing molten ferrochromium products lower in carbon than the ferrochromium employed in the mixtures, a portion of the carbon .being oxidized and eliminated by reaction with the oxidizing material. The reaction mixtures may includeone or more metals other than iron and chromium, a reducing agent such as silicon (in elemental form or in the form of ierrosilicon or rerrochrorne silicon, for example) and one or more reducible metal compounds.

.The reducing and oxidizing agents (including the carbon ofthe high-carbon Ierrochromium). are provided in such amounts and proportions as to develop suflicien't heat. to melt any metal present and toreduce the metal of reducible metal compounds present, with the production of molten metal, under the conditions under which the reaction mixtures are employed. Ac-

, cording to one phase of the invention, the reducing agents employed consist only or substantially entirely of the non-metallic elements, sili-' con and carbon. The oxidizing material employed may consist entirely of oneor more oxygen-bearing compounds of non-reducible metals (not reducible to the elemental state by the reducing agents employed and under the normal conditions employed in producing chromiumbearing alloys) such as alkali and alkaline earth metals; it may comprise one or more oxygenbearing compounds or reducible metals such as iron, chromium, nickel, cobalt, vanadium, tungsten, molybdenum, titanium and manganese; or it may comprise one or more oxygen-bearing compounds of non-reducible metals and one or more compounds of reducible metals. The reducible metals may be included in the reaction mixtures as metals (in elemental condition), as silicides or in the form of oxygen-bearing compounds.

The reaction mixtures of the invention are particularly suitable for use in altering the compositions of molten metal baths, as, for example, through incorporation therein or alloying elements like iron, chromium, nickel, copper, cobalt, vanadium, tungsten, molybdenum, titanium and manganese. They may be employed tor-altering the composition of molten metal when a final product of relatively high carbon content is to be produced. They may be used with particular advantage in foundry practice for altering the composition of molten iron for casting purposes. They may be used advantageously, also, in producing steel products of various compositions, and they may be employed directly to produce metal products containing various metals in about the proportions inwhich the metals are present in the mixtures (in the metallic state or as reducible metal compounds or both). When the reaction-mixtures are employed for altering the compositions of molten metals they preferably are caused to react on the surfaces of molten baths of the metals.

i after mixing with the other components. When all or a portion of the oxidizing material is employed in the solid state resulting from solidification from the molten state, it serves as bonding material for bonding together in intimate association the other components of the mixtures.

The solid components of the reaction mixtures which are not solidified from the molten state in forming the mixtures preferably are employed in the form of particles minus 100-mesh in size. Reaction mixtures in which oxidizing material is solidified from the molten state may be formed by mixing all components intimately and thereafter heating [the mixtures to temperatures above the fusing temperatures of one or more of the particular oxidizing materials or agents employed. The reaction mixtures may be formed into briquettes or agglomerates of suitable sizes and shapes prior to heating, or the fused, plastic or liquid masses may be cast or otherwise formed into agglomerates of any suitable sizes and shapes in any suitable manner.

When fusion is to be carried out, the cxidizing material should include at least one oxidizing agent having a fusing point below the temperature at which ignition of the mixture, with resulting reaction will take place. oxidizing agents having suitably low fusing or melting temperatures include many of the oxygen-bearing compounds of alkali metals such, for example, as sodium nitrate, sodium chlorate and sodium dichromate. Other oxidizing agents which may .be employed in forming the reaction mixtures include calcium chrcmate, sodium chromate and manganese dioxide.

According to one important aspect of the in vention, high-carbon ferrochromium is employed with suitable oxidizing material to form exothermic mixtures capable of reacting to produce molten ferrochromium containing carbon in lower proportions than in the ferrochromium employed in forming the mixtures. By reaction of the oxidizing agent with the carbon of the ferrochromium (and with the small amount of silicon usually present), all or a large proportion of the heat required for melting the iron and chromium of the ferrochromium is developed or generated. Such reaction mixtures may be caused to react directly on the surfaces of molten metal baths to effect alteration of the compositions of the metals of the baths or they may be caused to react directly, out of contact with molten metals, to produce ferrochromium of altered compositions with respect to carbon.

When the heat developed by reaction of the oxidizing agent with the carbon of the highcarbon ferrochromium is to be relied upon largely or substantially entirely for melting the iron and chromium of the ferrochromium, I prefer to employ ferrochromium containing more than six percent (6%) carbon by weight or even ferrochromium containing about eight to ten percent (8 to 10%) carbon by weight. Ferrochromium containing carbon in the range eight to ten percent by weight, when mixed intimately in finely divided condition with an oxidizing agent such as sodium nitrate or sodium chlorate, reacts rapidly upon ignition to form molten ferrochromium containing less than six percent carbon by weight. The carbon is oxidized preferentially and chromium recoveries readily exceed ninety percent.

In forming reaction mixtures containing highcarbon ferrochromium, I may rely entirely on the heat developed by reaction of the carbon of the ferrochromium with the oxidizing agent or I may incorporate in the mixtures small amounts of silicon which will function to aid in inhibiting oxidation of the chromium as well as in developing heat by reaction with the oxidizing agent. I prefer to employ some silicon in the mixtures when the ferrochromium employed contains less than about eight or nine percent carbon. Also, the presence of silicon is desirable when compounds of reducible metals are present in the mixtures with the ferrochromium and the oxidizing agent, as, for example, when the mixtures contain oxides of metals such as iron, copper and nickel and when the oxidizing materials employed include chromate compounds. The silicon employed may be present in the high-carbon ferrochromium as an alloy component, or it may be added in the form of elemental silicon or in the form of a silicide such as ferrosilicon, lowcarbon ferrochrome silicon or a silicide of an alloying element.

The following examples illustrate the production of molten ferrochromium of lowered carbon content by partial oxidation of the carbon of high-carbon ferrochromium, employing sodium chlorate in one case and sodium chlorate in conjunction with oxidized ferrochromium in the other. The oxidized ferrochromium is a product resulting from the oxidation of ferrochromium in the solid state and in the presence of one or more basic compounds such as lime and soda ash under conditions such as to produce a chromate-bearing product. Oxidized ferrochromium may be produced by roasting finely divided highcarbon ferrochromium (preferably minus mesh) with access of air at a temperature above about 1000 C. and below the fusing temperature of the ferrochromium.

The high-carbon ferrochromium used analyzed as follows:

Per cent Cr 66.4 C 8.2

Sodium chlorate was of commercial grade.

Oxidized ferrochromium was of the following composition:

Mixing and intimately grinding 100 parts of the high-carbon ferrochromium with 57.6 parts of sodium chlorate, and ignition of the mixture gave a very rapid reaction to fusion, leaving a ferrochromium product containing 63.8% Cr and 6% C.

A mixture containing 100 parts of the highcarbon ferrochromium, 65 parts of the oxidized ferrochromium and 29.6 parts of sodium chlorate reacted immediately to fusion and gave a ferrochromium product containing approximately 62% Cr and 4.8% C.

Oxidized ferrochromium for use in forming reaction mixtures in accordance with the invention may be produced according to any procedure outlined in my Patent No. 2,176,688.

The above examples serve to illustrate the reaction involvingpartial oxidation of carbon in high-carbon ferrochromium to produce a fused ferrochromium of lower carbon content.

when such an exothermic mixture is placed on a bath of molten iron, as, for instance, cast iron, it reacts rapidly to produce molten ferrochromium which enters the molten iron and adds chromium thereto without chilling the iron as whoteln high-carbon ferrochromium is added direc y.

amass The following example illustrates the commercial application of the reaction mixtures: To add to 1000 pounds of cast iron sufllcient chromium to give one percent (1%) chromium in the resulting casting, I add to the molten bath of iron 26.4 pounds of an exothermic mixture comprising 100 parts of high-carbon ferrochromium and 57.6 parts of sodium chlorate ground and intimately mixed (preferably 100-mesh or finer). The reaction is completed in a few minutes. I then remove the small amount of slag and cast the metal as usual. Upwards of 90% recovery usually is made.

Modification of the above procedure can be made with equally good results using, for example, other oxidizing agents, or combinations of oxidizing agents, and slag forming fluxes. A partial or complete oxidation of the loosely held carbon in the high carbon ferrochromium is all that is required to give sufficient heat to melt the iron and chromium of the ferrochromium.

The following examples illustrate the production and use of exothermic mixtures of the invention containing high-carbon ferrochromium, an oxidizing agent and added silicon for aiding in inhibiting oxidation of the chromium and in developing heat for melting the reaction products, the mixtures being employed for altering the composition of molten iron for casting by adding chromium thereto:

The ferrochromium employed contained 66.4 percent chromium and 5 percent carbon.

The silicon was employed in the form of ferrochrome silicon containing 61.5 percent silicon and 21.0 percent chromium.

Example A An exothermic reaction mixture was formed by grinding together 0.56 pound of the highcarbon ferrochromium, 0.34 pound of sodium nitrate and 0.14 pound of the ferrochrome silicon. The resulting mixture (in which the particles were substantially all minus 100-mesh in size) was heated to a temperature slightly higher than the melting point of the sodium nitrate. The fused mass thus produced was solidified in the form of a briquette which was added to a ladle containing twenty pounds of molten iron. Reaction was initiated immediately and completed in less than one minute.- The molten iron before alteration contained Per cent 0 3.14 Si 2.30 Mn 0.72 Cr 0.0

The altered metal product formed analyzed as follows, indicating a chromium recovery of about ninety-two percentv (92%) Per cent C 3.17 Si 2.37 Mn 0.66 Cr 1.84

Example B mediately and completed in less than one minute. The molten iron before alteration contained Per cent C 3.17 Si '2.22 Mn 0.73 Cr 0.0

The altered metal product formed analyzed as follows, indicating a chromium recovery of about ninety-four percent (94%):

The following examples illustrate the production and use of exothermic mixtures of the invention containing high-carbon ferrochromium, oxidizing agents, metallic alloying agents including copper, nickel and molybdenum and added silicon for aiding in inhibiting oxidation of the chromium and in developing heat for melting the reaction products and the metals present in the mixtures, the mixtures being employed for altering the compositions of molten iron products for casting by adding chromium and the metallic alloying agents thereto:

The ferrochromium employed contained 59.0 percent chromium and 8.2 percent carbon.

The silicon was employed in the form of ferrochrome silicon containing 61.5 percent silicon and 21.0 percent chromium.

Example C minute. The molten iron before alteration contained Per cent C 3.07 Si 2.24 Mn 0.74 Cr 0 0 Ni 0 0 The altered metal product formed analyzed as follows, indicating a chromium recovery of about 92% and a nickel recovery of about 95%:

Per cent C 3.03 Si 2.15 Mn 0.68 Cr 0.98 Ni 2.74

Example D An exothermic mixture was formed by grinding together 0.36 pound of the high-carbon ferrochromium, 0.26 pound of metallic copper in powder form, 006 pound of the ferrochrome silicon and 0.15 pound of sodium nitrate. The resulting mixture (in which the particles were largely minus -mesh in size) was fused and solidified as in Example A, and the briquette obtained was added to a ladle containing twenty pounds of molten iron. Reaction was initiated immediately and completed in about one-half minute. The molten iron before alteration contained Per cent C 3.08 Si '2.33 Mn 0.72 Cr 0.0 Cu 0.0

The altered metal product formed analyzed as follows, indicating a chromium recovery of about 90% and a copper recovery of about 98%:

Per cent C 3.10 Si 2.31 Mn 0.68 Cr 0.94 Cu 1.25

cient heat is developed to melt them. The upper limit of the sizes of any coarse particles employed will depend upon the capacity of the bonding material to retain them within the reaction zone during the course of the reaction.

This application is a continuatiOn-in-part of my copending application Serial No. 256,560,

,flled February 15, 1939.

I claim:

1. A solid agglomerate suitable for use in the production of molten metal by exothermic reaction comprising particles of high carbon ferrochromium intimately associated with and bonded together by means of oxidizing material solidified from the molten state and capable of reacting with carbon of the ferrochromium with the development of suflicient heat to melt the iron and chromium of the ferrochromium.

2. An exothermic mixture comprising (1) high carbon ferrochromium and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) alkali metal nitrate, (b) alkali metal chlorate and (c) alkali metal chromate, the components of the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned as to be capable of reacting upon ignition to generate suiiicient heat to melt the iron and chromium of the ferrochromium.

3. An exothermic mixture comprising (1) high carbon ferrochromium and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned as to be capable of reacting upon ignition to generate sumcient heat to melt the iron and chromium of the ferrochromium.

4. An exothermic mixture comprising (1) high carbon ferrochromium containing silicon and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned as to be capable of reacting upon ignition to generate suflicient heat to melt the iron and chromium of the ferrochromium.

5. An exothermic mixture comprising (1) high carbon ferrochromium, (2) silicon and (3) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components 0! the mixture being intimately associated with and bonded together .by means of the oxidizing material and being present in such quantities and being so proportioned as to be capable oi reacting upon ignition to generate suflicient heat to melt the iron and chromium of the ferrochromium.

6. An exothermic mixture comprising (1) high carbon ferrochromium, (2) metallic material other than high carbon ferrochromium, (3) silicon and (4) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (1)) sodium chlorate and (,e) a chromate of sodium, the components 01 the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochromium are capable of reacting upon ignition to generate suflicient heat to melt the metals present in the mixture.

7. An exothermic mixture comprising (1) high carbon ferrochromium, (2) one or more metals of the group consisting of nickel, cobalt, copper, vanadium, tungsten, molybdenum, titanium and manganese, (3) silicon and (4) oxidizing material containing a large proportion of a compound of the group consisting of (a) alkali metal nitrate, (b) alkali metal chlorate and (c) alkali metal chromate, the components of the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochromium are capable of reacting upon ignition to generate sumcient heat to melt the metals present in the mixture.

8. An exothermic mixture comprising 1) high carbon ferrochromium, (2) one or more metals of the group consisting of nickel, cobalt, copper, vanadium, tungsten, molybdenum, titanium and manganese, (3) silicon and (4) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of the mixture being intimately associated with and bonded together by means of the oxidizing material and being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochrcmium are capable of reacting upon ignition to generate sufficient heat to melt the metals present in the mixture.

9. An exothermic mixture consisting essentially of (1) high carbon Ierrochromium and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) alkali metal nitrate, (b) alkali metal chlorate and (c) alkali metal chromate, the components of the mixture being present in such quantities and being so proportioned that the oxidizing material and the carbon of the ferrochromium are capable of reacting upon ignition to generate suflicient heat to melt the iron and chromium of the ferrochromium.

10. An exothermic mixture consisting essentially of (1) high carbon ferrochromium and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of the mixture being present in such quantities and being so proportioned that the oxidizing material and the carbon of the ferrochromium are capable of reacting upon ignition to generate suificient heat to melt the iron and chromium of the ferrochromium.

11. A solid agglomerate suitable for use in the production of molten metal by exothermic reaction comprising particles of high-carbon ferrochromium, particles of a reducible metal compound and particles of non-carbonaceous reducing material capable of reducing to the metallic state the metal of the reducible metal compound intimately associated with and bonded together by means of oxidizing material solidified from the molten state in contact with said particles.

12. The method of producing a reaction mixture suitable for use in the production of chromium alloys which comprises oxidizing carbonbearing ferrochromium and forming an oxidized product low in carbon and containing iron and chromium in oxidized forms, and mixing the oxidized product in the solid state with (1) a solid silicon-containing reducing agent and (2) solid high-carbon ferrochromium.

13. A reaction mixture suitable for use in the production of chromium alloys which comprises (1) oxidized ferrochromium produced by oxidizing high-carbon ferrochromium and forming an oxidized product low in carbon and containing iron and chromium in oxidized forms, (2) a solid, silicon-containing reducing agent and (3) solid, high-carbon ferrochromium.

14. The method of reducing the carbon content of carbon-bearing ferrochromium containing more than about six percent of carbon which comprises forming an intimate mixture of the ferrochromium in finely divided form with a solid oxidizing agent capable of reacting exothermically with the carbon of the ferrochromium, and heating the mixture to a temperature sufiiciently high to initiate a self-propagating reaction between the oxidizing agent and the carbon of the ferrochromium.

15. An exothermic mixture comprising solid components consisting essentially of (1) high carbon ferrochromium containing silicon and more than about six percent of carbon and (2) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate (1)) sodium chlorate and (c) a chromate of sodium, the components of the mixture being present in such quantities and being so proportioned that the oxidizing material and the carbon and silicon of the ferrochromium are capable of reacting upon ignition to generate sufilcient heat to melt the iron and chromium of the ferrochromium and carbon being present in the ferrochromium in amount sufiicient to produce a substantial exothermic effect by reaction with the oxidizing material.

16. An exothermic mixture comprising solid components consisting essentially of (1) high carbon ferrochromium containing more than about six percent of carbon, (2) silicon and (3) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (1)) sodium chlorate and (c) a chromate of sodium, the components of the mixture being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochromium are capable of reacting upon ignition to generate suflicient heat to melt the iron and chromium of the ferrochromium and carbon being present in the ferrochromium in amount sufficient to produce a substantial exothermic effect by reaction with the oxidizing material.

17. An exothermic mixture comprising solid components consisting essentially of (1) high carbon ferrochromium containing more than about six percent of carbon, (2) metallic material other than high carbon ferrochromium, (3) silicon and (4) oxidizing material containing a large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of themixture being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochromium are capable of reacting upon ignition to generate suflicient heat to melt the metals present in the mixture and carbon being present in the ferrochromium in amount suflicient to produce a substantial exothermic effect by reaction with the oxidizing material.

18. An exothermic mixture comprising solid components consisting essentially of (1) high carbon ferrochromium containing more than about six percent of carbon, (2) one or more metals of the group consisting of nickel, cobalt, copper, vanadium, tungsten, molybdenum, titanium and manganese, (3) silicon and (4) oxidizing material containing a. large proportion of a compound of the group consisting of (a) sodium nitrate, (b) sodium chlorate and (c) a chromate of sodium, the components of the mixture being present in such quantities and being so proportioned that the oxidizing material and the silicon and the carbon of the ferrochromium are capable of reacting upon ignition to generate sufllcient heatto melt the metals present in the mixture and carbon being present in the ferrochromium in amount suflicient to produce a substantial exothermic efiect by reaction with the oxidizing material.

19; An exothermic reaction mixture suitable for use in the production of chromium alloys which comprises solid particles of carbon-bearing ferrochromium containing more than about six percent of carbon and solid oxidizing material capable of reacting exothermically with the carbon of the ferrochromium, the components of the reaction mixture being of such compositions and being present in amounts and proportions such as to efiect, upon ignition of the reaction mixture, oxidation and elimination of a portion of the carbon of the ferrochromium through reaction of the carbon contained therein with the oxidizing material and carbon being present in the ferrochromium in amount sufiicient to produce a substantial exothermic effect by reaction with the oxidizing material.

20. An exothermic reaction mixture comprising (1 solid high-carbon ferrochromium containing more than about six percent of carbon, (2) solid silicon-containing material and (3) solid oxidizing material capable of reacting exothermically with carbon and silicon, the components of the reaction mixture being of such compositions and being present in amounts and proportions such as to eii'ect, upon ignition of the reaction mixture, oxidation and elimination of a portion of the carbon of the ferrochromium through reaction of the carbon contained therein with the oxidizing material and carbon being present in the ferrochromium in amount surficient to produce a substantial exothermic effect by reaction with the oxidizing material.

MARVIN J. UDY. 

